# Geodesic models of quasi-periodic-oscillations as probes of quadratic gravity

## TL;DR

This paper proposes a method using geodesic models of QPOs to test quadratic gravity theories with future high-precision X-ray observations, potentially constraining deviations from general relativity.

## Contribution

It develops a novel approach combining relativistic precession and epicyclic resonance models to test quadratic gravity against observational data from future X-ray missions.

## Key findings

- Future X-ray instruments can measure QPO frequencies with sub-percent accuracy.
- At least two QPO triplets can constrain quadratic gravity coupling parameters.
- The method enhances the potential of QPOs as probes of strong-field gravity.

## Abstract

Future very-large-area X-ray instruments (for which the effective area is larger than $>3$m$^2$) will be able to measure the frequencies of quasi-periodic oscillations~(QPOs) observed in the X-ray flux from accreting compact objects with sub-percent precision. If correctly modeled, QPOs can provide a novel way to test the strong-field regime of gravity. By using the relativistic precession model and a modified version of the epicyclic resonance model, we develop a method to test general relativity against a generic class of theories with quadratic curvature corrections. With the instrumentation being studied for future missions such as eXTP, LOFT, or STROBE-X, a measurement of at least two QPO triplets from a stellar mass black hole can set stringent constraints on the coupling parameters of quadratic gravity.